Differential effects of nitric oxide on the responsiveness of tactile hairs.

The responses of tactile hairs located on legs of the desert locust Schistocerca gregaria (Forskål) are modulated by nitric oxide (NO). There are two types of tactile hair on the tibia of the hind leg of the locust which differ in their thresholds for mechanical stimulation, their location on the leg and in the effect of NO on their responses to deflection. The spike response rates of mechanosensory neurons of low-threshold hairs decreased when exposed to elevated NO levels caused by perfusion of the leg with saline containing the NO donor PAPANONOate. In contrast, in high-threshold hairs, which show low responsiveness under control conditions, an increase in spike rates was observed during PAPANONOate application. These opposing effects of NO reduce the differences in the spike responses of the two types of tactile hairs to mechanical stimulation and are likely to have an impact on behaviours elicited by mechanical stimulation of the legs.